Materials used in electrolytic aluminum production cells, also known as Hall-Héroult cells, must be thermally stable at high temperatures on the order of 1,000° C., and must be capable of withstanding extremely harsh conditions such as exposure to molten cryolite, molten aluminum, and oxygen at elevated temperatures. Although various types of materials have been used as cathodes and to line the walls of electrolytic aluminum production cells, a need still exists for improved materials capable of withstanding such harsh conditions.
Titanium diboride (TiB2) would be desirable for use as a cathode material in electrolytic aluminum production cells. When titanium diboride is used as a wettable cathode, the energy used for operation of the cell can be greatly reduced. Titanium diboride has many desirable properties including wettability by molten aluminum, high temperature stability and exceptional corrosion resistance. However, the manufacture of the titanium diboride cathodes is difficult because titanium diboride powders are not easily sintered and do not readily form dense parts. Titanium diboride powders often require the application of very high pressures and temperatures well in excess of 2,000° C. in order to decrease porosity of the sintered material. Even at such extreme conditions, titanium diboride components are often not fully dense or they exhibit microcracking, both of which decrease performance.
Sintering aids have been added to titanium diboride in attempts to decrease processing temperatures, microcracking and residual porosity. However, conventional sintering aids have been found to decrease the corrosion resistance of titanium diboride components, particularly in harsh environments such as found in electrolytic aluminum production cells.